It uses a sum total of one pin; GPIO 18. This is the data pin, it also uses 5V and GND but since they’re not IO pins it doesn’t matter. You can take the hat right off the Pi and drive it from an Arduino if you wanted.

If you want to drive it from the Pi you can probably use 3 jump wires; make sure you plug them into the header and not the little breakout contacts on the side of the HAT though. Unicorn Hat has logic level conversion for the Pi onboard.

Apologies for hijacking this thread, but it seems like an appropriate place to ask. Which of the pins are used/not used on the dot3k? Are the sca and sdl pins free? Or could one piggyback onto them anyway?

I’ll try and whip up more precise instructions for you! It should be doable ( it’s no different from putting it straight on the Pi ) but you need to connect the right wires to the right places for it to work.

I’m very new, but have a question. This thread makes it sounds like I can run the Unicorn Hat via wires. Would I be able to run multiple Unicorn Hats from one Pi by connecting them all to the same pin on the Pi? Looking to have a little fun in my office at work! My coworkers have been spending hundreds of dollars on Hue lights. Unicorn Hat seems cooler!!!

The external power makes a huge difference when the brightness is at 1.0 and most of the display is lit up. Before when I was displaying white at full bright, it was more of a yellow, now it is very white.

Unicorn HAT only runs from Pin 18 using some highly specific signal generation code- the Pi is technically not capable of pushing this sort of signal out on any other pin. You can connect two to this pin, but they will display the same thing.

The normal way of connecting multiple devices with these kind of LEDs is to “daisy chain” them, one after the other. The trouble is, we’ve not provided an “OUT” on the Unicorn HAT so you can’t easily do this.